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I will be ostracized because of this
|--+--Herrerasauridae (or "herrerasaurids")
| |=="primitive segnosaurs" (?)
| |--Therizinosauridae (_Segnosaurus_, _Nanshiungosaurus_, etc.)
Note that several authors have cited the short ilium, pes with
metatarsal I reaching the tarsus, and vestigal remnant of metatarsal V as
basis for making Theropoda exclusive of herrerasaurids. Theropods have a
relatively long ilium characterized by a long preacetabular process
(Paul, 1988; Glut, 1997). Currie (1997) characterizes theropods as having
a strap-like scapula. This is seen in advanced herrerasaurids, but not in
_Eoraptor_ (as reconstructed by Paul in Benton, 1997). Indeed, the
scapula of _Eoraptor_, as reconstructed, does not differ significantly
from that of primitive archosauriforms like _Euparkeria_ (as
reconstructed by Paul in Parrish, 1997). It seems possible, then, that
advanced herrerasaurids might have developed the strap-like scapula
independently of theropods.
Morphology of the foot and pelvis of therizinosaurids might place them
descendants of a line that gave rise to sauropodomorphs and then later
ornithischians. The therizinosaurid line would represent a state more
derived than than those "segnosaurs" which gave rise to sauropodomorphs
and primitive to the "segnosaurs" which were the direct ancestors of
ornithischians. The basal "segnosaurs" might have been more derived than
_Eoraptor_, but primitive to _Staurikosaurus_ based on comparisons of the
pelvis and skull in these two forms as compared with the relatively
derived _Segnosaurus_ and "prosauropods".
Morphology of the coracoid of _Therizinosaurus_ seems to be
similar to that of _Herrerasaurus_ itself (based on several photographs
As for _Alxasaurus_:
As described in Glut (1997) and Maryan'ska (1997), there is no way to be
certain that _Alxasaurus_ is a therizinosaurid. Skull material is lacking
and the portion of the dentary might well be pre-oviraptosaur. The
anterior edge of the ilium is unknown as is the pubis. The ischium
(again, as restored) is reminiscient of an oviraptorsaur. The neural
spines on the cervical vertebrae appear to be more reduced than in
supposedly more primitive therizinosaurids. This animal is damaging to my
case for a "segnosaur" origin of phytodinosaurs, but mostly because my
information about the pes is limited and I must rely solely on a single
reconstruction reproduced twice.
I'm sure that this post will never be read by most of you, you probably
see the "absurd" clagogram at the top and dismiss me as an idiot. For
those of you who do actually read the whole thing, thank you for your
indulgence. I appreciate your giving me a chance and I will accept your
criticisms (harsh as you wish, if you've read the whole thing) or your
indignant refusal to respond to such "nonsense." I think I've made a
decent case--FIRE AT WILL!!!
Benton, M.J. (1997). "Origin and early evolution of dinosaurs." In:
Farlow, J.O. and Brett-Surman, M.K. (eds.) _The Complete Dinosaur_.
Indiana University, Bloomington. pp. 204-215.
Carpenter, K., and Currie, P.J. (1990). "Summary and prospectus." In:
Carpenter, K. and Currie, P.J. (eds.) _Dinosaur Systematics: Approaches
and Perspectives. Cambridge University Press, New York. pp. 309-314.
Glut, D. (1997). _Dinosaurs: The encyclopedia_. McFarland & Company,
Inc., Publishers, Jefferson.
Maryan'ska, T. (1997). "Segnosaurs (therizinosaurs)." In: Farlow, J.O.
and Brett-Surman, M.K. (eds.) _The Complete Dinosaur_. Indiana
Press, Bloomington. pp. 234-241.
Parrish, J.M. (1997). "Evolution of the archosaurs." In: (see above).
ALSO CHECK OUT T. MIKE KEESEY'S WEBSITE FOR THE CURRENTLY ACCEPTED
CLADISTIC ANALYSIS OF ALL DINOSAURS: